{"id":"CVE-2026-31709","revision":null,"records":[{"revision":"3f8af6fbb69c4c508f3d7c8b6c1d8129","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-31709","aliases":[],"title":"smb: client: validate the whole DACL before rewriting it in cifsacl","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: validate the whole DACL before rewriting it in cifsacl\n\nbuild_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a\nserver-supplied dacloffset and then use the incoming ACL to rebuild the\nchmod/chown security descriptor.\n\nThe original fix only checked that the struct smb_acl header fits before\nreading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate\nheader-field OOB read, but the rewrite helpers still walk ACEs based on\npdacl->num_aces with no structural validation of the incoming DACL body.\n\nA malicious server can return a truncated DACL that still contains a\nheader, claims one or more ACEs, and then drive\nreplace_sids_and_copy_aces() or set_chmod_dacl() past the validated\nextent while they compare or copy attacker-controlled ACEs.\n\nFactor the DACL structural checks into validate_dacl(), extend them to\nvalidate each ACE against the DACL bounds, and use the shared validator\nbefore the chmod/chown rebuild paths. parse_dacl() reuses the same\nvalidator so the read-side parser and write-side rewrite paths agree on\nwhat constitutes a well-formed incoming DACL.","state":0,"publishedAt":"2026-05-01T13:56:06.522+00:00","modifiedAt":"2026-10-19T19:06:06.98+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/smb/client/cifsacl.c\"\n ],\n \"versions\": [\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"b8603d9ae6c9087662b098619996bc4a8064319d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"c2abdebf72000a64603ced84d36ccbd164f11391\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"d92f3f0b22414e7515696a02224d0af55e3004a3\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"b78db9bddc84136f6a0bb49e8883cf200dfb87a8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"bc3e9dd9d104ca1b75644eab87b38ce8a924aef4\",\n \"lessThan\": \"0a8cf165566ba55a39fd0f4de172119dd646d39a\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/smb/client/cifsacl.c\"\n ],\n \"versions\": [\n {\n \"version\": \"5.12\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"5.12\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.210\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.176\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.140\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.86\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.35\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.2\",\n \"lessThanOrEqual\": \"7.0.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","score":8.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/b8603d9ae6c9087662b098619996bc4a8064319d","https://git.kernel.org/stable/c/c2abdebf72000a64603ced84d36ccbd164f11391","https://git.kernel.org/stable/c/8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12","https://git.kernel.org/stable/c/d92f3f0b22414e7515696a02224d0af55e3004a3","https://git.kernel.org/stable/c/ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5","https://git.kernel.org/stable/c/b78db9bddc84136f6a0bb49e8883cf200dfb87a8","https://git.kernel.org/stable/c/0a8cf165566ba55a39fd0f4de172119dd646d39a"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31709","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-31709","identifiers":["CVE-2026-31709"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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